Over 6 feet tall, large leaves, red stalk...weed?

So I'm brand new to gardening and put in three Revolution Pepper plants. Two of them seemed to be doing well and now one of them looks like the pictures below. I think I've successfully grown a very happy and healthy weed. Am I correct? If so, what kind of weed is this?

I think you are absolutely correct. Thank you! It makes me a little sad as it is obviously growing much better than anything else in my fledgling garden!

I suppose I'll chop her down tonight. Do you think I can just cut it down to a stump to be rid of it or do I need to remove the root? It's planted very close to a fruitful pepper plant and I'd hate to damage it in the process.